Bitcoin has the critical mass going for it, with many merchants accepting bitcoin for example as well as other companies creating easier methods of buying and selling.
This critical mass is important. For most on the cutting edge of development, they can only really concentrate effectively on one coin so as not to dilute their efforts. For the near future at least, it appears that Bitcoin is it.
I would tend to go along with this. Bitcoin is way out in front, so far in front of the rest that it would be hard to imagine any of the rest catching it now. However, I am also acutely aware that practically none of the big internet based companies that were around during the tech bubble, are market leaders these days or even still around. Without knowing a great deal about the technology I don't suppose it would be beyond the realms of possibility that there turns out to be some design flaw in Bitcoin that eventually renders it untenable over the long term. Perhaps the computational power required to keep the Bitcoin universe functioning will become to great or perhaps someone will crack the algorithm and start forging coins. Who knows, but history tells us that
New Invention mk1, never lasts the duration and improvements are always required for a concept or technology to succeed.
Who knows, perhaps one of the pump n dump coins will be in a good position to take Bitcoin's place should anything bring it down for whatever reason, or more likely is, that the Google or Facebook of crypto-currency is not yet with us.